Refrigerating system



REFRIGERATING SYSTEM Filed Feb. 8, 1944 2 sheets-sheet@ `Vigil.

Ihvehtov: Harold F'. Lathrop,

Nov. 6, 1945. A H, F. LATHROP 2,388,556

REFRIGERATING SYSTEM Filed Feb. 8, 1944 2 Sheets-Sheet 2 Inventow-z HaT-old. F. Lathrop, v

His Attorheg.

l "It is an o bfectloi my mvention.to.

Patented. Nov. 6, 1945 eral Electric Company, a` corporationV Nevv.

Applicationrebruarys,1944; `sei-nino; 521,518 u jffsciaims. (citez-"115i"` My invention relates to refrigeratingsystems and `particularly` to multi-stage?compression refrigerating systems for producing `very`V low temperatures.

Refrigerating systems provided# with rmultistage compressorsfmaybeyemployed vto obtain ,very low temperatures i 4which `are necessary; for example, to cool testing y 1- ooms for equipment which mustbe operated at such low temperatures.-4 Multi-stage ,reirigerating systems vmay be provided,with devices,for cooling:thecom f Pressed refrigerant dichargedrOm-the low pressur@ Compressor betere, itentersotnemtake ofthe higher; Pressure `=f `1wnnr sS01:in ordern remcve `excess superheat from the-low pressure gas, The

temperature!- of, the `discharge gastifrom V,the low pressure compressor may be lovverl ythanthat of 'the cooling Waters available for cooling the, main condenser so` that itfcannot be ,cooledvbysthe water; in such casesrin .order tocool thelgas nowing .from the low pressure compressor to the high pressure compressor, it becomesldesirable t0, apro?- -vvide a device lutilizing a" portionof` the refrigerant for` cooling the between; stages.

frovidefa multistagef refrigeratiigv system" linclu'din'g'g an improved arrangement for cooling the'refrigerant gas. between the 1 ow, .pr essureandhigh pressure stages' and `for controlling 'the interstage cooling t obtainfmaxir'nurnft "tivenessfjof the" system. i ,n V `i It is another object.' of ,my invention .t0r4 provide af refrigeratingl 'system including lbvif land `high pressure cmnpression` stages yincludingan ".im- 1 proved arrangement for cooling', or subcoolirig the liquid refrigerantiairiilffor vcontrolling "the amount of superheat in "thef refrigerant entering the higher pressure`stage.`j Y

Further objects 'and Aativan tages of my invennon wm become; apparent as the fouo'winedescription proceeds, and thef` features lof novelty which characteriseN `my inventionfvvill' be pointed out with partiuiarity inthe claims 'annexed to and forming afpart of this fspecication.' MFor a betterfgiinderstanding ot my invention reference maybe-had tothe accompanying draw'- ings in which Fig.L 1 `il'lustraits diagrammatcally a two-stage'v compression* refrigerating system embodying rnyinvention', and Figs. 2, 3 and 4 illustrate refrigeratingsy'stexns similar to that of Fig. 1' and'inl ding `modified forms of my invention. i f

Briey, therefrigeratingsystems illustrated in cylinders arranged` to operate at `different pressures and connected in series -in-a refrigerant circuit including a condenser, a liquid receiver, and an evaporator' controlled vby a thermostatic expansion-valve. The refrigerant circuit includes compartmentm'` chamber "H". 1The evaporator is connectedin' the .circuit of a refrigeratingsystem includingalow;l pressure compressor l2; a high pressurecompressor i3, aicondenser I 4, and `'a liquid' receiver i5. .The compressors` i l 2f and I3 mayube .separately drivenor Imay comprise high and flow stage `cylinders -ofV1 'a" *single compressor,

these' alternativeconstructions being well known in the art. The condensewidfisprovided With a cooling water casing I6, andthe cooling water absorbsheat `from thefhot compressed refrigerant'` i'nthefcondenser Ml thereby condensing andzliquef-ying the refrigerant which -lows into the liquid receiver. 1l 5. t Liquid' refrigerant from the receiver Iflowslthrougha-liquidline including a heat `exchangecoil-i'Vanda liquid sub'- coolerr coil I8. Ther ow of "liquid refrigerant throughthe liquid line is'` controlled-by a pressure regulating valve ligand aathermostatic expansion valve'f20 having a 'control bulb 22 responsive to the temperature `of thel"refrig'erant With'- drawn from thelevaporatorf lill@"l'll'ie pressure regulatingvalv'e-flS is'providedffi'n-lorder to reduce the pressure of therrefrigerant'-before it passes to the thermostatio" expansion f valve' 20; this valve is `desirable i particularly. Vwhen ithe evaporator I IJ is being operatedat-the lower-feridof` the temperature Vrangel of the i system; -f The lcold vaporized refrigerant, together Withj'any particles of liquid withdrawn from the evaporator'- 0,1ows through a casing 23 lin .heatfexoha'nge relation with the coil l1 and thereby .cools the? `liquid Irefrigerant in thecoil Hi; Jthefcasing:anclfcoil` thus constitute the main or"liquici linetosuction':line heat exchanger. Theheatff'romWhe-l u'id refrigerant Vaporizes 'anylliquid `remaining in the suction gas lbefore it -flows lfrom-"tiielieat'exchanger 'to the intake of the compressor 12gy In orderflto subcoolthellquidonitspathtotheevaporator I3 aheatexchangeiacketisarranged aboutthe liquidcoil IIandlssupplledwithaportionof the liquid refrigerant cooled in the coil I1 and withdrawn from the liquid line through a connection 23 under control of a valve 21. After nowlng through the jacket 23 and subcooling `the liquid in the coil I3 the refrigerant is returned to an interstage connection or conduit 23 between the compressors I2 and I3. 'Ihe refrigerant after coolingthesubcooleristhenavailabletocoolthe refrigerant flowing from the compressor cylinder I2 to the compressor cylinder I3 and thereby reduces the ammmt of superheat in the refrigerantin the interstage connection 23. A considerable` increase in eifectiveness of the refrigerating system maybe obtained by reducing the superheat in the interstage connection, and in order to obtain the required low temperature, it may be desirable to employ as much as ten per cent of the refrigerant circulated through the low pressure stage.

In order to control the amount of cooling of the refrigerant in the interstage connection 23, I provide the valve 2l with a temperature responsive element or feeler bulb 33 which is retakenfmmtheliquidlineataT-connection 33 beforethellquidflowatothecoilllintheheat exchanger casing23 whereas in the arrangement -speciilcallyinacopendingapplicationofwayne sponsive to the temperature of the refrigerant Y main liquid to suction line heat exchanger Hf the subcooler coil I3, and the temperature control of the refrigerant in the interstage connection 23 increases the capacity and improves the efllciency of the system and facilitates the attainment of the very low temperatures required.

The modification of my invention illustrated inFig.2issimlartothatshowninFigZ land corresponding parts have been designated by the same numerals. The evaporator I3 and cooling chamber II together with the valves I3 and 23 have been omitted; however, they are innded to be employed in the same manner as in Eg. 1. In the system of Fig. 2 the operation of the liquid subcooler comprising the coil I3 and the jacket 25 is controlled by `a thermostatic expansion valve 3| having a feeler bulb 32 responsive to the temperature of the vapor-ized refrigerant withdrawn from the jacket 25. element (not shown) responsive to the pressure in the jacket 25 and is eiectve to control the superheat of the vaporized refrigerant leaving the subcooler in a manner well known in the art. In order to control the temperature of the low pressure refrigerant admitted to the compressor I3, a temperature responsive valve 3'3 is provided to control a bypass connection 33 for admitting liquid refrigerant from the liquid line directly to the interstage connection 23. The valve 33 is controlled solely in response to the temperature of the refrigerant entering the compressor I3 through the agency of a temperature responsive element or feeler bulb 35 secured in heat exchange relation with the connection 23 at the intake of the compressor I3. The liquid refrig- The valve 3l includes an Y E. Dodson, Serial No. 521,520. iiled February 8,' 1944,andassignedtothesameasthe system of Fig. 1, with the exception that the pressure regulating valve I3v can be omitted, since the liquid enters the thermostatic expansion valve 2l at an intermediate pressure prevailing between the low and high pressure compressors. Liquid refrigerant expands, vaporines, and is cooled upon entering a thermally insulated container or chamber 3l. The vapor or flash gas isdrawnoifthroughatubenandisconducted to the intcrstage connection 23. Cold liquid refrigerant accumulates in the lower portion of the container 3l, until it is withdrawn through the tnermostatic expansion valve 23, and therefrom fed into the evaporator I3. The ilow of refrigetant to the chamber 31 is controlled by a temperature responsive valve I3 having a feeler bulb 3| responsive to the temperature of the refrigerant admitted to the compressor I3. It will -readily be apparent that the operation of the valve 33 will determine the height of the liquid `refrigerant in the chamber 3l. 'lhe cooling of the liquid refrigerant in the chamber 31 is, of course, effected by the vaporlmtion of a portion of the refrigerant under the operation o'f the com' presser I3 in withdrawing vapor through the tube 33.

The refrigerang system illustrated in Pig. 4 employs a refrigrant circuit similar to that of Fig. 1 except that the main liquid line to suction line heat exchanger and the liquid subcooler have beenarrangedinacommonreceptaclenillled with suitable heat insulation. The main heat exchangercomprisesacasingahavingabeat exchange coil Ila arranged therein. InV order to provide liquid subcooling a portion of the liquid line I3a between the coil Ila and the evaporator issurroundedbyatubeorlacketaandthe concentric tubes are wound about the casing 23a but not in contact therewith. Liquid refrigerant from the receiver Il is circulated throughthecasingaunder controlofthetemperature responsive valve 21a having its thermal element 33a arrangedv to be responsive to the temperature of refrigerant admitted to the compresser I3. Refrigerant vapor-ized in the casing 25a is returned to the interstage connection 23 for removing superheat from the refrigerant discharged from the compressor I2. The operation ofthesystemofFig.4isessentiallythesameas that of Fig. 1; however, the arrangement of the heat exchanger and subcooler in the insulating casing l2 makes it possible to provide a heat exchangeunitasaseparateelementofthesystem erantsuppliedtothevalves3Iand33in1iig.2is 75 andto employ tbesame insulation forprotecting both the heat exchangers from the higher temperature of the ambient air.

During the operation of the refrigerating systems illustrated in the several figures of the drawings, the temperature of the refrigerant flowing from the low pressure stage into the intake of the high pressure stage is controlled to increase the capacity and efciency of the system and, furthermore, the efficiency is further increased by effective subcooling of the liquid refrigerant. These arrangements are simple and effective and greatly facilitate the efficient operation of the system at low temperatures.-

' While I have described my invention in connection with a two-stage compressor system for cooling an enclosed chamber other applications will readily be apparent to those skilled in the art. I do not. therefore, desire my invention to be limited to the particular constructions illustrated and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

- What I claim as new and desire to secure vby Letters Patent of the United States is:

1. A multi-stage refrigerating system comprising high and low pressure compressors, an evaporator and a condenser, an interstage connection for conveying refrigerant from the outlet ofsaid low pressure compressor to the inlet of said high pressure compressor, means for conducting liquefied refrigerant from said condenser to said evaporator, means for removing a portion of the refrigerant from said last mentioned means and for returning it to said interstage connection, and

means dependent solely upon the temperature of 4. A multi-stage refrigerating system comprising high and low pressure compressors, an evaporator and a condenser, an interstage connection for conveying refrigerant from the outlet of said low pressure compressor to the inlet of said high pressure compressor, a liquid line for conducting liquefied refrigerant from said condenser to said evaporator, means including a first heat exchanger for utilizing vaporized refrigerant returned from said evaporator to said low pressure compressor for cooling refrigerant in said liquid line, a second heat exchanger arranged to -cool liquid refrigerant in a portion of said line between said first heat exchanger and said evaporator for subcooling the liquid refrigerant in said portion of said line, means for bleeding refrigerant from said line to supply said second heat exchanger and for conducting' to said interstage connection the refrigerant vaporized in said second heat exchanger, and means responsive to the'temperature of the l refrigerant at the inlet of said high pressure the refrigerant at the inlet of said high pressure l compressor for controlling the quantity of refrigerant admitted to said interstage connection.

2. A; multi-stage refrigerating system comprising high and low pressure compressors, an evaporator and a condenser. an interstage connection for conveying refrigerant from the outlet of said low pressure compressor to the inlet of said high pressure compressor, means including a liquid refrigerant cooler for conducting liquid refrigerant from said condenser to said evaporator, said cooler being arranged to utilize aportion of the liquid refrigerant in said conducting means for cooling the liquid in said cooler and for thereafter conveying said portion to said interstage connection, and means dependent solely upon the temperature of the refrigerant at the inlet of said high pressure compressor for controlling the quantity of refrigerant admitted to said interstage connection.

3. A multi-stage refrigerating system comprising'high and low pressure compressors, an evaporator and a condenser, an interstage connection for conveying refrigerant from the outlet of said low pressure compressor to the inlet of said high pressure compressor, a liquid line for conducting v compressor for controlling the bleeding'of refrigerant to said second heat exchanger.

5. A multi-stage refrigerating system comprising high and low pressure compressors, an evaporatorand a condenser, an interstage connection for conveying refrigerant from the outlet of said low pressure compressor to the inlet of said high pressure compressor, means including' a liquid cooler arranged between said condenser and said evaporator for conducting liquid refrigerant from said condenser to said evaporator, said cooler comprisingla container arranged to collect liquid refrigerant and to separate gaseous refrigerant from the liquid therein, a conduit opening into said container below the top thereof for conveying refrigerant from said container to said interstage connection, and a valve between said condenser and said container and dependent solely upon the temperature of the refrigerant entering said high pressure compressor for-controlling lthe flow 4of refrigerant to said container to maintain at a predetermined temperature the refrigerant admittedto said high pressure compressor.

6. A multi-stage refrigerating system comprising high and lowpressure compressors, an evaporator and a condenser, an interstage connection for conveying refrigerant from the outlet of said low pressure compressor to the inlet of said high pressure compressor, a liquid line for conducting the liquefied refrigerant from said condenser to said evaporator. said liquid line including two heat exchange portions in series, a casing surrounding said irst portion and connected in the path of vaporized refrigerant returned from said evaporator to the inlet of said low pressure compressor, a Jacket surrounding said second portion of said line to form a concentric tube heat exchanger, said Jacket with said second portion HAROLD F. LATHROP. 

